Vol. 79, No. 1: 51-61, 2010 ACTA SOCIETATIS BOTANICORUM POLONIAE 51 THE HYBRID ORIGIN OF CALAMAGROSTIS ×GRACILESCENS (POACEAE) IN POLAND INFERRED FROM MORPHOLOGY AND AFLP DATA BEATA PASZKO1, MARCIN NOBIS2 1 W. Szafer Institute of Botany, Polish Academy of Sciences Lubicz 46, 31-512 Kraków, Poland e-mail:
[email protected] 2 Department of Plant Taxonomy and Phytogeography, Jagiellonian University Kopernika 27, 31-501 Kraków, Poland (Received: March 23, 2009. Accepted: January 18, 2010) ABSTRACT The morphology of Calamagrostis canescens and C. stricta recorded in the Ma³opolska Upland (the vicinity of Zbijów Ma³y, ca. 10 km northeast of the town of Skar¿ysko-Kamienna, Central Poland) was examined due to in- termediate individuals found in sympatric populations of these species. Both putative parents as well as individu- als that appeared hybrid-like were found in an extensive, wet hay-meadow. Various vegetative and reproductive characteristics were studied to identify hybrids. Interestingly, Polish accessions of C. ×gracilescens exhibited so- me degree of morphological intermediacy but resembled C. stricta in spikelet morphology. Branching of the mid- culm, the number of nodes per culm, callus hair length and relative callus hair length are the best characters to di- stinguish the Polish C.×gracilescens. AFLP analysis proved to be suitable for detecting recent hybridization events between C. canescens and C. stricta. Analysis of the Bayesian clustering analysis showed that C. ×gracile- scens were subjected to gene flow from the C. canescens gene pool as well as from the C. stricta gene pool. KEY WORDS: Calamagrostis ×gracilescens, C. canescens, C. stricta, hybrid, habitat conditions, mor- phology, AFLP markers, gene flow.